separating signal from noise

Archive for October, 2008

I’ve heard that the average number of sexual partners that men have is 8 while the average number of sexual partners that women have is 6. But if you stop and think about these numbers, they don’t make sense.

It’s easier to think of these numbers as frequencies, because humans have a frequentist number sense. Suppose there is a population of 10 men and 10 women, and, simplifying the case momentarily, men only have sex with women and vice versa. In that population, the total number of unique sex interactions for the men would be 10 * 8 = 80. The total number for the women would be 10 * 6 = 60. If men are only having sex with women, you can see how this is impossible. With whom did the men have 20 extra sexual encounters?

Well, in a realistic setting, same-sex encounters happen. But, while I’m willing to grant that men may have more same-sex encounters than women, they don’t have 30% more (an average of 8 is about 30% more than an average of 6). Maybe 10% of men and 5% of women have same-sex encounters, so at most the discrepancy is 5%. In truth, I don’t think it’s even that much. I think men and women probably have similar rates of same-sex encounters, which means those encounters add roughly the same amount to each average.

So again, where does this 30% discrepancy between the reported average of 8 and the reported average of 6 come from? I think it comes from reporting errors. One possibility is that men are falsely increasing their sex partner count while women are falsely decreasing it. Maybe the actual average for men and women is 7 and they are on average reporting one higher and one lower. I can understand why this would happen in a society where men are encouraged to boast about their sexual encounters while women are encouraged to downplay them.

Another possibility is that the word “sex” is not clearly defined. Men may count, for example, every oral sex encounter as a sex encounter, while women don’t. If 15% of sex encounters are oral sex, that accounts for the 30% disparity. That’s a simplified case again. I’m sure the actual numbers are more complicated, but you get the point in terms of errors (or at least discrepancies) in reporting.

One way or another, I don’t believe what men and women report when the averages are 8 and 6. I believe the averages are — in fact must be — almost exactly the same, except perhaps for a few percentage point difference with regard to same-sex encounters.

Communists excuse the failures of communism by claiming that “true” communism has never existed, as if that isn’t strong evidence that their ideal can never be achieved (hundreds of millions of people tried it for 40-60 years; if that’s not good evidence, I don’t know what is). And now we see the failures of the market, not because we did or didn’t interfere with the market in certain ways, but because the market, when left to its own devices, doesn’t produce the longterm outcomes that we desire.